I'm using OpenSMTPD for my mail server which is a pleasure compared to Sendmail. At times in my maillog there are attempts made to relay mail from various IPs. Can I add a rule like the one below to stifle any further attempts from that IP? I realize the IPs may and probably will change, but I'd like to add any extra protection I can. I'm currently blocking IPs from N Korea, China, and certain other countries.